Solid oxide fuel cells have properties such as high power generation efficiency, low emission of SOx, NOx and CO2, good responsiveness to a fluctuation of load, and compactness. Thus, solid oxide fuel cells are expected to be applied to various power generation systems such as large-scale centralized type, suburban distributed type, and home power generation systems, as an alternative for thermal power generation. Under such situation, ceramics have been mainly used for parts for solid oxide fuel cells, such as separators, interconnectors and current collectors, since the parts are required to have good oxidation resistance, good electrical conductivity, and thermal expansion coefficient close to those of electrolytes and electrodes at a high temperature around 1000° C.
However, ceramics have poor workability and are expensive. Furthermore, an operation temperature of solid oxide fuel cells has been reduced to around 700 to 900° C. in recent years. Thus, studies have been actively made to use metallic materials for parts such as separators since metallic materials are less expensive and have better workability and oxidation resistance than ceramics.
The metallic parts for solid oxide fuel cells are required to have excellent oxidation resistance. The applicant has proposed ferritic stainless steels with excellent oxidation resistance in JP-A-2007-16297 (Patent Literature 1), JP-A-2005-320625 (Patent Literature 2), and so on.